Remove runtime.LockOSThread() call from kuryr-cni

runtime.LockOSThread() was a leftover from initial CNI plugin skeleton.
It is only required when CNI plugin does the netns operations. Our
plugin isn't doing that as it's kuryr-daemon that is responsible for
that.
Also the imports are now in nicer order.
Change-Id: I1d7ee6a8fec104fd09094a49304a4c22b419cf3a